It is well known that tractor-trailer type truck assemblies, also commonly called "rigs", have the tendency to jackknife especially upon sudden stops, radical turns such as to avoid for instance collision and on slippery roads, resulting in the driver's loss of control over such a rig and possibly causing damage to the rig, other vehicles or injury or even death to driver and others. Many means have been suggested in the past to overcome or to at least minimize such jackknifing tendency, yet, none of these past attempts are believed to represent true remedies of the problem. The following references of interest provide an overview of typical devices offered in the past:
U.S. Pat. No. 903,884 (Przygode) teaches a motion checking device comprising a lever system leading to a piston and throttle arrangement designed to resist sudden motion of trailer with respect to tractor. PA0 U.S. Pat. No. 2,461,212 (Hanna) describes a mechanically activated cylinder system to control the swing of trailer vehicles by the driver. PA0 U.S. Pat. No. 2,470,383 (Wakeman) deals with device for stabilizing trailers consisting of a bracket attached to the front of the trailer which rests between a pair of convex discs mounted on the tractor, said discs being connected with pistons slidably mounted within cylinders, the latter containing hydraulic fluid; the rate of flow of the fluid can be restricted. PA0 U.S. Pat. No. 2,565,285 (Wakeman) uses essentially the same principle as the above Wakeman reference except that the bracket is mounted on the tractor activating a piston and cylinder system attached to the trailer. PA0 U.S. Pat. No. 2,709,088 (Orbits) suggest an anti-jackknifing system based on one or more piston-and-cylinder assemblies attached to the end of the tractor and to the underside of the trailer body. PA0 U.S. Pat. No. 2,773,702 (Safko) is concerned with an anti-jackknifing device which when activated forces a pin from the trailer underbody into the slotted portion of the so-called fifth wheel thus restricting the movement of the trailer. PA0 U.S. Pat. No. 3,850,449 (Link et al.) provides an anti-jackknifing device based on a piston-cylinder arrangement either restricting the motion of the trailer by being attached either to the fifth wheel or to the front of the trailer, the other end being connected with the tractor.
None of the above devices seem to have either fulfilled their expected purpose or were found acceptable by the trucking industry either for reasons of practicality, cost, or both.